The correlation between HbAlc and risk-associated outcomes demonstrated in the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study (UKPDS) underscores the need to measure HbAlc with sufficient reliability such that clinical laboratory results can be directly related to these studies and, therefore, to the risk for development or progression of diabetes-related chronic complications. A lack of comparability of HbA I c test results among methods and laboratories is a major obstacle to the effective implementation of a national and global strategy to reduce the complications associated with diabetes through proper glycemic control.